Widespread throughout the state, tolerant of silt and warmer temperatures

General Description

This is a very widespread and tolerant mayfly species with triangular operculate gills on the second abdominal segment. Large hatches of this prolific mayfly ("tricos") can be seen in the silted sections of the Missouri, Yellowstone and Clark Fork River Basins. In fact all major river systems provide habitat for this ubiquitous mayfly if silted pool areas provide habitat. This species of mayfly increases in abundance when streams become silted, dewatered and warmer.